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Large Kaikoura aftershock still possible

A major aftershock following last year’s Kaikoura earthquake remains “well within the probabilities”, according to modelling by New Zealand’s GeoNet.

There is a 15% chance of one or more 6-6.9-magnitude quakes within the next month, GeoNet says in its latest assessment, issued last week. The risk has eased from 18% in last month’s outlook, but remains about five times greater than normal expectations.

GeoNet says 14,796 quakes have occurred since the 7.8 Kaikoura event in November. Of those, four were of magnitude six or greater and a further 56 ranged from 5-5.9.

The aftershocks have mostly been in a broad area from North Canterbury through to Cook Strait, which separates the North and South islands.

Aftershock probabilities in Christchurch, hit by major quakes in 2010 and 2011, are not greatly affected by the Kaikoura event, GeoNet says.